Piping systems are used in structures to supply liquids and gasses and to-carry sewage and other wastes away. Common household piping or plumbing systems include water supply piping, drain piping, and possibly gas piping. Water supply pipes carry water from a water supply pipe to plumbing fixtures such as sinks, baths and showers, toilets, sprinkler systems, spigots, and the like. Drain piping carries human wastes, ground garbage from disposers, and waste water to sewers or septic tanks. Gas piping, if present, carries fuel gases such as natural gas or propane gas to appliances such as furnaces, ranges, gas fireplaces, and the like. A particularly necessary quality of all types of piping is integrity of the pipes and joints such that the liquids or gases carried do not leak.
In order to ensure that a piping system does not leak, pressure testing is often conducted and may be required by some local codes. Plumbing is preferably installed, tested, and joints repaired, as needed, prior to closing access to the piping and joints by the installation of wallboards. Testing often involves pressurizing the piping system with compressed air, or alternatively filling it with water, and detecting any leaks. Testing is usually done before any fixtures, appliances, or the like have been connected to the piping system.
Plastics, such as PVC or polyvinyl chloride and others, are used in many types of plumbing, including waste plumbing. It is common practice, during testing, to install removable test plugs or caps on pipe stubs to which fixtures, such as toilets, will be subsequently connected. After testing is completed, the caps are removed. The test caps need to be sealed in place such that they do not leak during testing. When the test caps are no longer needed, they need to be removed in such a manner that the test cap is not lost in the waste plumbing, such that the remaining plumbing is not damaged by removal of the test cap, and such that no remaining parts of the test cap assembly interfere with the fixture to be installed. Additional features which would be desirable in such a test cap include the capability of conveniently connecting a source of pressurized fluid to the cap and resealable structure for conveniently testing that the piping system is pressurized.